Adjustable step mold with product release means

ABSTRACT

This mold utilizes opposed movable unitary sides defining respective outer shell components in combination with a fixed inner core to form a cement receiving casting cavity into which there is placed a vertically adjustable floor plate assembly selectively arrangeable to produce castings of different numbers of steps as desired within the maximum capacity of the mold. The outer shells are hingedly affixed at their lower ends to a support frame and are movable, preferably by mechanical means, outwardly in unison away from the casting for separation therefrom and during such movement, suitable adjustable abutment means on the lower ends of the shells engage the underside of the floor plate to elevate the casting sufficiently to release it from the inner core. Means are provided to conveniently adjust the mold for casting a selected number of steps and risers and variations for the size of the platform of the mold and a novel bracket holder is provided for suitably holding handrail anchor bolts and nut in the wet cement until it hardens.

United States Patent 1191 Lister 1451 Sept. 17, 1974 v [22] Filed:

[ 1 ADJUSTABLE STEP MOLD WITH PRODUCT RELEASE MEANS Jan. 29, 1973 [21] Appl. No.: 327,746

[52] US. Cl 249/14, 249/74, 249/91,

249/162 [51] Int. Cl B28b 7/22 [58] Field of Search 249/14, 74-75,

FOREIGN PATENTS OR APPLICATIONS 192,928 11 1907 Germany 249 75 Primary ExaminerRobert D. Baldwin Assistant Examiner.1ohn McQuade Attorney, Agent, or Firm-Morton S. Adler [5 7] ABSTRACT This mold utilizes opposed movable unitary sides defining respective outer shell components in combination with a fixed inner core to form a cement receiving casting cavity into which there is placed a vertically adjustable floor plate assembly selectively arrangeable to produce castings of different numbers of steps as desired within the maximum capacity of the mold. The outer shells are hingedly affixed at their lower ends to a support frame and are movable, preferably by mechanical means, outwardly in unison away from the casting for separation therefrom and during such movement, suitable adjustable abutment means on the lower ends of the shells engage the underside of the floor plate to elevate the casting sufficiently to release it from the inner core. Means are provided to conveniently adjust the mold for casting a selected number of steps and risers and variations for the size of the platform of the mold and a novel bracket holder is provided for suitably holding handrail anchor bolts and nut in the wet cement until it hardens.

4 Claims, 15 Drawin g Figures Y PAIENIED 7 saw r 5 3;aas'. 1 0s PATENTEU SEN 71974 SHEET 3 OF 5 EEI ADJUSTABLE STEP MOLD WITH PRODUCT RELEASE MEANS BACKGROUND OF THE INVENTION This invention relates to improvements in the art of precasting concrete into a monolithic flight of steps and further expedites and simplifies the techniques disclosed and discussed in my prior US. Pat. No. 3,281,110. As revealed in such patent and in the sev eral references cited, particularly those to Kogl, a pioneer in this art, the precasting of concrete step units requires various mold components including an outer shell, an inner core, a back gate and riser and tread assemblies which must be assembled, disassembled and rearranged according to the number of steps in different castings. Various interlocking devices have been used for the several parts and in the repeated use of such molds, experience has shown that problems of proper alignment frequently arise due to wear and tear of the parts and because of the number of parts involved, the problem of keeping time and labor costs within profitable ranges is a continuing consideration.

Accordingly, with the above observations in mind, it is one of the important objects of this invention to provide an improved mold for precasting concrete step units which will materially expedite and facilitate the handling and manipulation of the several mold components and substantially reduce the requirement and necessity for labor personnel having a high degree of expertise.

More particularly, it is an object herein to provide a mold of the above class wherein the outer shell members are hingedly affixed at one end to a support frame in a position assuring proper alignment with an inner core and does not entail displacement of the type that would require, repeated assembly and adjustments.

A further object is to provide a mold as characterized which includes improved and simplified means for accommodating the casting of step units with different desired numbers of treads and risers and platform sizes.

Still another object is the provision of novel means for freeing the casting from the outer shell members and inner core simultaneously so that it may be removed from the mold.

A still further object is to provide improvements in means for supporting handrail anchor bolts and nuts within the wet cement until it has hardened.

SUMMARY A hollow inner core or shell having a top, sides, open bottom and a stepped configuration on one end serves as the inner portion of this mold and is secured to a suitable base or support frame. The outer portion of the mold is proved by opposed outer shell members of unitary construction which have a stepped configuration on corresponding ends complementary to that on the inner core. The outer shell members are hingedly secured at their respective lower ends to the support frame and means are provided to secure them in appropriate spaced relationship to the inner core to form a casting cavity.

A raisable floor plate or pallet is positioned on the frame at the bottom of the cavity at each side of the inner core to serve as a closure for the cavity at such point and adjustment means permit supplementary pallets to be supported by the base pallets at different planes of vertical spacing corresponding to the level of different tread positions whereby the number of treads and risers in a particular casting can be selectively determined within the maximum capacity of the mold. Removable tread and riser components forming an outer shell for the stepped portion are attachable to the stepped portion of the mold by simple clamp devices and a novel handrail anchor bolt and nut holding clamp is designed for use with the stepped portion. A back gate mountable on the inner core has depending legs positionable within the casting cavity whereby the position of the gate determines the size of the platform on the finished casting.

Mechanical means are preferably provided for simultaneously moving the outer shell members outwardly on their hinge points to free it from the casting and the lower ends of such outer shell members are provided with suitable abutment means which engage the underside of the pallets as the outer shell members move about their hinge point whereby the pallets are slightly raised and correspondingly raise the casting to free it from the inner core so that it can be removed from the mold. The means for moving the outer shell members outwardly is also capable of returning them to their proper spacing and alignment relative to the inner core for purposes of another casting.

The several objects of this invention together with the general details outlined and the advantages of the same will be more fully described in relation to the more detailed description of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of this new mold shown in assembled position and illustrating an alternative position in broken lines of the back gate together with a showing of one of the tread plate removed;

FIG. 2 is a side elevational view of the mold shown in FIG. 1;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1 with the floor plate or pallet in the casting cavity shown in broken lines at different levels of position relative to different numbers of steps to be cast;

FIG. 4 is a cross sectional view of the inner core taken on the line 44 of FIG. 3;

FIG. 5 is a foreshortened rear elevational view of this mold showing the back gate but with the mechanism for moving the outer shell members removed;

FIGS. 6, 7 and 8 are respective elevational views, partly in section, illustrating the adjustable supports for the supplementary pallets at different levels of vertical spacing;

FIG. 9 is a cross sectional view of the back gate taken on the line 9-9 of FIG. 5;

FIG. 10 is a perspective view of one of the friction clamps used to temporarily secure certain of the mold components;

FIG. 11 is a fragmentary perspective view of one of the step portions of this mold showing the handrail anchor bolt holding device attached thereto;

FIG. 12 is a cross sectional view of FIG. 1 I and showing in addition the holddown plate and wing nut used with the anchor bolt holding device;

FIG. 13 is a cross sectional view taken on the line l3-13 of FIG. 12;

FIG. 14 is a rear elevational view illustrating the mechanism for opening and closing the outer shell members relative to the inner core with the solid lines representing the closed or casting position and the broken lines representing the open or casting removal position; and

FIG. 15 is a side elevational view of the mechanism shown in FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, this new mold is designated generally by the numeral 16 and is shown in FIG. 1 assembled and ready for use. While the several components of this mold will be described in detail as this description proceeds, for purposes of a general outline and understanding, such mold 16 includes a roller wheel mounted base frame or support 18 to which there is secured an inner core 20 and opposed sides 22 and 24 which constitute the outer shell members and are pivotally secured at their lower ends to frame 18 for cooperative association with the inner core 20 as will later appear. Included also are removable tread plates 26 and riser plates 28, adjustable floor plates or pallets 30 and 32, an adjustable back gate 34 and a handrail anchor bolt holding device 36 (FIGS. 11-13) for use while the wet cement is setting.

Frame 18 includes a base preferably in the form of a pair of elongated spaced parallel beams 38 and 40 for which I preferably have use 2 X 3 inch metal tubing (FIG. 14) and transversely arranged on the beams 38 and 40 so as to be elevated from the supporting surface for beams 38 and 40 are the several like pairs of closely spaced and parallel cross members 42, also preferably made from 2 X 3 inch metal tubing. The several pairs of cross members 42 as seen in FIGS. 2 and 3 include one pair at the respective end portions of the frame beams 38 and 40 with the other pairs disposed at equally spaced positions longitudinally of the frame. The length of such cross members is such that they project perpendicularly or laterally a predetermined distance from the respective beams 38 and 40 as can be seen in FIGS. 4 and and serve as a support for the sides 22 and 24 as will appear. The base members 38 and 40 of frame 18 are preferably mounted on suitable caster wheels 44 for obvious reasons although this is not necessarily required.

The inner core or inner shell 20 (FIGS. 3 and 4) is a one piece hollow member preferably of ten gauge steel having a top 46, sides 48 and 50, openat the bottom and back and having the stepped configuration 52 at the front for a predetermined number of steps which is here shown as four including the top or platform atep but which may, of course, be made to provide for a maximum number of steps either less than or greater than the number shown here. The sides 48 and 50 are inclined from the vertical slightly inwardly from bottom to top as best seen in FIG. 4 and the bottom end portions of sides 48 and 50 are welded to the angle members 54 which in turn are welded to the cross members 42 and thus provides a secure and permanent attachment of the inner core 20 to the frame 18.

The sides 22 and 24 serve as the outer shell to complement the inner core 20 and since such sides are of like construction, only one will be described in detail and like parts will be given like numerals. Thus, with reference to side 22 for description, such side comprises an elongated rigid panel or plate 56 having a stepped shape 58 on one end corresponding to portion 52 of the inner core 20 and to the outer face of panel 56 there is welded a plurality of vertically disposed stiffeners or posts in the form of metal tubes 60 which are spaced longitudinally of panel 56 so that the lower end of each tube 60 is disposed intermediate a respective pair of cross. members 42 (FIG. 1) where the lower ends of such tubes extend below the cross members 42 to approximately the plane of the bottom of beams 38 and 40 as seen in FIG. 4. The upper edge portion of panel 56 is flared slightly as at 62 and is bordered by the angle strip 64 along the top and similar angle strip portions are provided on each riser and tread section on the stepped portion 58 of panel 56. The inner surface of panel 56 is provided with a plurality of vertically spaced horizontal ribs 66 to produce a design feature which is not material to the present invention. Thus far described, it will be appreciated that the sides or outer shell members 22 and 24 are each a unitary component comprising the panel 56, posts 60 and angle strips or lips 64 and the association of these outer shell members 22 and 24 with the frame 18 and inner core 20 is one of the more important novel features of this invention as will become apparent.

With each side 22 and 24 arranged relative to frame 18 as seen in FIG. 1 where each tube 60 is disposed between a pair of cross members 42 as described, such sides are pivotally attached to frame 18 at their lower ends by means of an elongated rod 68 extending through all pairs of cross members 42 and each of the posts 60 as seen in FIGS. 1 and 2. The respective ends of rod 68 are threaded as at 70 to receive the retaining nuts 72 at respective ends in a well known manner. Thus arranged, the sides 22 and 24 are movable on rod 68 as the pivot or hinge point from a vertical or upright position to a substantially horizontal position represented by the respective solid and broken lines in FIG. 14 and their upright position as seen in FIG. 4 they will be in appropriate spaced relationship to the sides 48 and 50 of the inner core 20 to form the casting cavity 74 (FIG. 1) into which the cement 76 (FIG. 4) can be introduced in any well known manner.

On that part of each post 60 which depends below cross members 42 there is journalled a transverse abutment member shown preferably in the form of bolt 78 with the bolt head 80 on the inner or back side of post 60. Nuts 82 are provided on bolt 78 on both sides of post 60 whereby the bolt head 80 can be selectively adjusted relative to its spacing from the inner or back side of post 60 for purposes which will be referred to in more detail in describing the operation and use of this mold.

With the outer shell members 22 and 24 pivotally associated with frame 18 as described and in their upper or vertical position, the several treads 26 and risers 28 are connected in a well known manner to the stepped portions 58 of the outer shell members 22 and 24 as best seen in FIGS. 1-3. For this purpose, the treads and risers are provided with appropriate apertured edges and end flanges which mate in part with each other and with the lips 64 on the outer shell members and while bolts and nuts are commonly used to secure such parts, I prefer to use an easily attachable and removable clamp 84 (FIG. 10) which includes a pin 86 to pass through the registering apertures of the parts to be secured and a channel body 88 to frictionally embrace the abutting flanges or edges. Such a type clamp 84 which I described in my Pat. No. 3,281,110 is simple, easy and quick to apply or remove and saves considerable time. Thus arranged, the casting cavity 74 is enclosed relative to the step portions as will be apparent.

The floor plates or pallets 30 and 32 are in the form of elongated rigid bars and are raisably positioned at each side of the inner core at the bottom of cavity 74 so as to rest on the cross members 42 as seen in FIG. 4. In this way, pallets and 32 are supported only at spaced points so that access to the pallets is unobstructed from the underside except at the point of the cross members 42 and the area intermediate each pair of cross members 42 provides an access path to the pa]- lets 30 and 32 for the movement of the bolt heads 80 as will later appear. The width of pallets 30 and 32 is such that it coincides with the width of the cavity 74 at its lower point so that for all practical purposes, fresh concrete is suitably retained and such pallets 30 and 32 serve as a base when the casting is to have the full complement of steps and risers for which the mold is de signed. Should a lesser number of steps and risers be desired, such as three, two or one in the illustrations shown, an additional or supplementary pallet 30' is used as best seen in the broken lines of FIG. 3. For this purpose, and for a three step casting for example, a number of support standards 90 (FIG. 6) are placed in cavity 74 on pallets 30 and 32 so that there is one of 30 such standards over one of the cross member beam in each pair 42. Standard 90 comprises an elongated hollow body 92 with an enlarged head plate 94 to support pallet 30 at the appropriate level. For a two step casting as may be seen in FIG. 4, standard 90 is slip-fitted in a suitable manner to an extension support 96 (FIG. 7) and for a one step casting, a second extension support 98 (FIG. 8) is used. It will thus be understood that the bottom or floor level of cavity 74 is elevated to correspond with the level of the number of steps desired and that the pallet 30' used for the several respective ascending levels will be respectively wider than those used at lower levels because of the small but progressively wider dimension of cavity 74 towards its upper extremity.

With the treads 26 and risers 28 attached to the outer shell members 22 and 24 and the appropriate pallets 30,32 or 30 in place as described, the assembly of mold 16 for casting purposes is completed by placement of the back gate 34. Such gate is of a general inverted U shape having vertically disposed spaced parallel legs 100 and 102, preferably of channel material, which are connected intermediate their upper extremities by the cross member 104 which is also preferably of channel material. A rubber gasket 106 (FIG. 3 and 9) conforming in shape to the U outline of members 100, 102 and 104 is placed in juxtaposition therewith on the inner side. It is secured in place by a generally matching inverted U shaped member comprised of the cross bar 108 to register with rail 104 and the integral depending wedge shaped flanges 110 and 112 to mate respectively with the back gate legs 100 and 102. Gasket 106 is secured to the back gate by bolts and nuts 114 as seen in FIGS. 5, 9 and 14. Thus arranged, it is pointed out that gasket 106 is made so that it extends slightly beyond the outer side extremities of the back gate legs 100 and 102 as indicated at 116 in FIG. 9.

Gate 34 is placed astraddle the inner core 20 (FIGS. 5 and 14) so that the legs and 102 are disposed within the cavity 74 and rest on the pallets 30, 32 or 30' whichever is used. The wedge flanges and 112 are disposed relative to the inner edges of legs 100 and 102 and serve to close the area between the straight sides of such legs and the inclined inner core sides 48 and 50. The position of the back gate 34 longitudinally of the inner core 20 is determined by the size of the platform desired. Such gate, for example, is shown in FIG. 1 in solid lines at the rear for a full platform and in broken lines for a platform of lesser dimensions. Once positioned, gate 34 is anchored in place when the outer shell members 22 and 24 are secured to the inner core 20 by bolts 118 as seen in FIGS. 1 and 4. For this purpose, suitable nuts 120 are welded to the inner side of inner core sides 48 and 50 to avoid the time and difficulty that would otherwise be encountered in securing bolts 118 as shown. As such bolts are tightened, the projecting edge of gasket 106 will be compressed so that gate 34 is adequately anchored for the intended casting.

With mold 16 constructed and assembled as thus far described, it will be understood that the fresh cement is introducted into cavity 74 at the top where it will not only form the sides but will fill the cavity portion 74 on the stepped portion as seen in FIG. 3. It will also be noted that the top plane of the outer shell members 22 and 24 is somewhat higher than the plane of the top 46 of the inner core 20 and the cement extending across the top 46 forms the platform of the finished casting. After the mold is filled and while the cement is still wet, the platform surface can be trowelled and the tread plates 26 are removed to permit the tread surface to be trowelled and to install the anchor bolt holders 36 (FIGS. 11-13) if desired. Holder 36 is generally of flat bar material of a T shape having the cross portion 122 and the depending portion 124. Portion 122 is placed in juxtaposition to strip 64 of side 22 and one end of 122 is pivotally attached to strip 64 by a removable pin 126 whereby portion 124 can be swung into juxtaposition with the wet cement on the step as seen in FIG. 1 l. Portion 124 is provided with one or more U notches 128 and with an upstanding threaded bolt shank 130. One or more railing anchor bolts 132 with nuts 134 attached are placed in the wet cement 76 as best seen in FIG. 12 and so located that the heads 136 rest over the U notch portions 128 on member 124. A retaining cap or plate 138 is placed over bolt heads 136 so as to rest on member 124 (FIG. 13) and is provided with a hole 140 through which bolt extends to receive the wing nut 142. By this arrangement, nuts 134 are held in proper position until the cement has set and when this has occurred, the wing nut 142 and retaining plate 138 are'removed so that the holder 36 can be pivoted out of association with bolts 132. Thereafter, such bolts can be removed, when desired, and nuts 134 remain firmly anchored to receive bolts 132 at such time as a handrail (not shown) may be mounted to the step structure.

The separation of the mold from the finished casting after it has properly set is one of the important features of this invention and in describing the same, reference is made more particularly to FIGS. 4, l4 and 15. At the rear of mold 16 there is provided an upstanding support member 144 secured to the rearrnost pair of cross members 42 and centrally located relative to a vertical center line through the inner core 20. A horizontal shaft 146 is journalled in support 144 and carries a large gear wheel 148 disposed at the rear of mold 16 as shown. A crank member 150 with a handle portion 152 is rotatably attached to support 144 below shaft 146 and carries a pinion gear 154 in meshing contact with gear 148 as best seen in FIG. 14. A rigid operating rod 156 is pivotally connected at one end 158 to the rear post 60 on the outer shell member 22 and extends across the rear face of gear wheel 148 where its other end 160 is similarly attached to such wheel near the perimeter. A like operating rod 162, similarly attached, has end 164 pivotally secured to the rear post 60 on outer shell member 24 and its opposite end 166 pivotally secured to the rear face of gear wheel 148 near the perimeter and when the mold 16 is inits casting position or what might be termed its closed position, it will be noted in FIG. 14 that this is represented in solid lines where rods 156 and 162 are substantially horizontal and parallel and that the points of connections 160 and 166 on the gear wheel 148 are at generally opposite points on the perimeter relative to shaft 146 although slightly offset from a direct diametrical alignment. In this position, the outer shell members 22 and 24 are in their fully closed position where they are secured for casting purposes by the bolts 118 as previously described.

To separate mold 16 from the casting, it will be understood that bolts 118 and all clamps 84 are removed together with the several tread plates 26 and riser plates 28. When this has been accomplished, crank handle 152 is manually rotated counterclockwise whereby the gear wheel 148 is turned in a clockwise direction causing rods 156 and 162 to move from the solid line position to the broken line position illustrated in FIG. 14. As this occurs, it will be apparent that rods 156 and 162 are simultaneously exerting an equal pushing force on the outer shell members 22 and 24 to pivot them on rod 68 away from the casting and it should be mentioned that the cavity surfaces of the mold will have been properly treated or coated in a well known manner to facilitate the separation.

As the outer shell members 22 and 24 are thus swung outwardly on their pivoted or hinged end, the bolt heads 80 on bolts 78 at the bottom of the several posts 60 will move through the access path intermediate cross members 42 to engage the bottom of the pallets 30 and 32 as represented by the broken lines in FIG. 14 and as the outer shell members 22 and 24 are full extended or opened, pallets 30 and 32 will be slightly raised or elevated along their length to correspondingly elevate the casting with equal and simultaneous force at each side of the inner core sufficiently to separate the casting from the inner core. For this operation, the adjustability of bolts 78 referred to permits the proper arrangement and alignment of the bolt heads 80 to assure their simultaneous contact with pallets and 32.

Only a slight elevation of the casting is necessary to separate it from the inner core 20 on the order of approximately one and one half inches and this is amply provided in the arrangement described. With bolts 78 in close proximity to the pivot or fulcrum point repre- I described. While this invention is not concerned with the removal of the casting once it has been separated from the mold, it will be understood that this is accomplished in any well known manner including the use of hoists and the like. With the casting removed, the rotation of crank handle 152 in a clockwise direction will return the outer shell members 22 and 24 to the solid line position in FIG. 14 and it will thus be appreciated that in the construction and use of this mold, the outer shell members, while movable, do not require disassembling or dismantling but remain at all times in a fixed association with the mold frame and the inner core and are therefore always in proper alignment when moved to and from their closed position.

The structure described for simultaneously separating the casting from the inner core and the outer shell members is believed to be a substantial improvement and innovation in the art of casting cement steps and materially reduces the time and costs heretofore required for such purposes. While I have shown a manually operated mechanism, it will be appreciated that the same can be power operated and other similar devices utilized within the concept here disclosed. Accordingly, from all of the foregoing, it is thought a full understanding of the construction and operation of this invention will be had and the advantages of the same will be appreciated.

I claim:

1. A mold for precasting a monolithic concrete stair structure, comprising:

a frame defined by:

parallel spaced beams,

a plurality of pairs of closely spaced transverse cross members secured to said beams in a uniform spaced relationship intermediate the ends thereof, and

said respective pairs of cross members each projecting perpendicularly from each respective beam,

an inner core defining a top, sides and a stepped portion on one end and secured to said frame,

a pair of like panel outer shell members for complementary cooperation with said inner core having respective top and bottom edges and disposed respectively at opposite sides of said inner core and each being pivotally secured at a point near their bottom edges to said frame so as to be movable on their pivot points to an upright or closed position for casting purposes and to a substantially horizontal or open position for removal of the casting,

removable fastening means for securing said outer shell members to said inner core in their closed position in a predetermined spaced relationship defining a respective casting cavity at each side of said inner core,

tread and riser plates removably attached to said respective outer shell members in complementary relationship to the stepped portion of said inner core to define a casting cavity thereat,

a respective pallet raisably positioned on said frame at the bottom of each cavity intermediate a respective inner core side and complementary outer shell member to serve as a base floor support for the casting,

a plurality of spaced vertically disposed posts secured to said outer shell members so that their respective lower ends are disposed between and extend below a projected end of a pair of cross members,

an abutment member on the bottom of each post disposed transversely of the longitudinal axis thereof, and

each projecting pair of cross members providing an access path for said respective abutments t the underside of said pallets whereby as said outer shell members are moved on their pivots points from closed or upright position to a substantially horizontal or open position for separation from the casting, said abutment members will move through a respective access path to engage and bear against the underside of said pallets to effect the uniform elevation of said pallets throughout their length to a higher plane and thereby correspondingly elevate a finished casting sufficiently to separate it from said inner core.

2. A mold as defined in claim 1 including means movably mounting said abutment members to said posts for selective adjustment relative thereto whereby said abutment members can be individually aligned for simultaneously engaging said pallets upon movement of said outer shell members.

3. A mold as defined in claim 1 including means moved simultaneously and uniformly from their closed to open position and effect the corresponding simultaneous and uniform elevation of said pallets.

4. A mold as defined in claim 1, including:

said inner core and outer shell members being designed to form a predetermined maximum number of treads and risers,

a plurality of vertically adjustable support members disposed on said respective pallets in longitudinal spaced relationship thereon,

a respective supplementary pallet disposed on each support member at corresponding planes above said pallets in the bottom of the casting cavity to provide alternate base floor supports for a selected number of treads less than the maximum, and

said supplementary pallets being correspondingly uniformly elevated with the elevation of the first mentioned pallets by the movement of said outer shell members. J 

1. A mold for precasting a monolithic concrete stair structure, comprising: a frame defined by: parallel spaced beams, a plurality of pairs of closely spaced transverse cross members secured to said beams in a uniform spaced relationship intermediate the ends thereof, and said respective pairs of cross members each projecting perpendicularly from each respective beam, an inner core defining a top, sides and a stepped portion on one end and secured to said frame, a pair of like panel outer shell members for complementary cooperation with said inner core having respective top and bottom edges and disposed respectively at opposite sides of said inner core and each being pivotally secured at a point near their bottom edges to said frame so as to be movable on their pivot points to an upright or closed position for casting purposes and to a substantially horizontal or open position for removal of the casting, removable fastening means for securing said outer shell members to said inner core in their closed position in a predetermined spaced relationship defining a respective casting cavity at each side of saiD inner core, tread and riser plates removably attached to said respective outer shell members in complementary relationship to the stepped portion of said inner core to define a casting cavity thereat, a respective pallet raisably positioned on said frame at the bottom of each cavity intermediate a respective inner core side and complementary outer shell member to serve as a base floor support for the casting, a plurality of spaced vertically disposed posts secured to said outer shell members so that their respective lower ends are disposed between and extend below a projected end of a pair of cross members, an abutment member on the bottom of each post disposed transversely of the longitudinal axis thereof, and each projecting pair of cross members providing an access path for said respective abutments to the underside of said pallets whereby as said outer shell members are moved on their pivots points from closed or upright position to a substantially horizontal or open position for separation from the casting, said abutment members will move through a respective access path to engage and bear against the underside of said pallets to effect the uniform elevation of said pallets throughout their length to a higher plane and thereby correspondingly elevate a finished casting sufficiently to separate it from said inner core.
 2. A mold as defined in claim 1 including means movably mounting said abutment members to said posts for selective adjustment relative thereto whereby said abutment members can be individually aligned for simultaneously engaging said pallets upon movement of said outer shell members.
 3. A mold as defined in claim 1 including means mounted to said frame in operable association with each outer shell member whereby with all fastening means relative to said outer shell members and said inner core removed, said outer shell members can be moved simultaneously and uniformly from their closed to open position and effect the corresponding simultaneous and uniform elevation of said pallets.
 4. A mold as defined in claim 1, including: said inner core and outer shell members being designed to form a predetermined maximum number of treads and risers, a plurality of vertically adjustable support members disposed on said respective pallets in longitudinal spaced relationship thereon, a respective supplementary pallet disposed on each support member at corresponding planes above said pallets in the bottom of the casting cavity to provide alternate base floor supports for a selected number of treads less than the maximum, and said supplementary pallets being correspondingly uniformly elevated with the elevation of the first mentioned pallets by the movement of said outer shell members. 